The present invention relates to the field of tissue products for sanitary or domestic use and is aimed in particular at products in rolls, such as rolls of bathroom tissue (or toilet paper) and the like.
The subject of the present invention is a roll made up of items based on (or essentially made of) a cellulose-fiber product. More specifically and according to an embodiment, the subject of the invention is a roll in which certain sheets, and more specifically in which each sheet of which it is made, has particular features associated with its thickness and its tensile strength.
Products of the aforementioned type packaged in the form of rolls are already known, in general. In these rolls, the sheets of product to be dispensed are customarily rolled onto a central core of cylindrical cross section made of cardboard or the like. In the field in question, the rolled sheets of interest to the user are conventionally made from cellulose-fiber products made of (or predominantly made of) tissue and assembled in the form of one or more bonded superposed plies, it being possible for the sheets to be separated from one another, in the direction perpendicular to the direction in which the sheets are unrolled, along perforated, so-called precut, lines allowing one or more sheets to be torn or removed from the roll.
In the case of rolls of multi-ply sheets, the various superposed plies are, depending on the use for which the sheet is intended and/or on the requirements dictated by the consumers and/or production constraints, held together more or less securely depending on the various techniques used to assemble the plies.
Most often, the plies in a multi-ply product made essentially of tissue are associated by applying an adhesive between the plies. The adhesive bonding is performed using any adhesive product generally used in the field of sanitary and domestic papers for combining plies with one another, such as, for example a polyvinyl alcohol in aqueous solution. This association by adhesive bonding may be combined with another type, which is also conventional, of combination of plies which is purely mechanical and consists in locally deforming the plies by crushing them so that the plies, imbricated in one another under the pressure of a cylinder, are held together once the association operation is over.
Upwards of a certain number of plies that need to be associated, particularly when more than three plies or groups of plies are to be associated, various kinds of problems may arise.
First of all, there are purely technical problems of associating the plies. There are various known ways of overcoming these. However, in most cases, the thick sheets are not flexible. “Thick” here means “more than 0.75 mm thick”.
Furthermore, it is known that the thickness may detract from the bond between the successive sheets, at the precut lines which usually form the connection between the sheets that form the roll. Problems of breakage here have already been observed: for example, the sheets become detached from one another while they are still on the roll itself.
Surprisingly and unexpectedly, the rolls according to the invention do not display such disadvantages.
Furthermore, sheets that are excessively rigid are unsuitable for use as bathroom tissue.
Incidentally, as far as the making of rolls is concerned, the sheets of which the rolls are formed need to be able to be rolled up easily, even at the center of the roll where the radius of curvature is the smallest.
Another parameter that is very important to applications to bathroom tissue has to do with the thickness and the strength, in the dry state, of the sheets of which the roll is formed.